ATHENS, Dec 20 (Reuters) - Greece must regain market confidence as soon as possible and before an available cash buffer is depleted, the country’s central bank said in a monetary policy report on Thursday. Greece and its lenders have built a 25-billion euro cash buffer, a safety net for the country which emerged from its third international bailout in August. “The existing cash buffer gives the Greek state the advantage of not having to attempt an immediate return to international markets through new bond issues. In no way, however, does this justify complacency,” the central bank said. It also said that Greece’s economy is expected to grow by 2.1 percent this year, by 2.3 percent in 2019 and by 2.2 pct in 2020, urging the country to continue implementing reforms with “unwavering resolve.” (Reporting by Angeliki Koutantou and Renee Maltezou)